I have imagined a possible Goodbye Whale Island scenario.
Episode begins with Gon and Killua deciding to head to Yorknew to pursue Greed Island. Gon tells Killua that he needs to say Goodbye first, because he doesn't know when he will be back. Killua understands. Gon runs off into the forest alone, while Killua packs up preparing to leave. In the forest Gon whistles and Kon appears and bear hugs him. Gon explains to Kon that he is a Hunter now and has to go find his father, as a Hunter he can no longer be friends with Kon and besides he has to leave, this time maybe for good, he doesnt know. He says farewell to Kon and begins to run off with a sad expression on his face. Gon flashes back and remembers 3 years ago he was attacked by a fox bear, but was saved by a man named Kite. He chose to save the baby fox bear (which turns out to be the one he just talked to). Kite explains that Ging is his mentor and that his greatest goal is to find him. Kite tells Gon that the best hunters are loved by animals. Return to present time and Gon tells Killua he is ready to go, Killua and Gon say goodbye to Aunt Mito and Gon and her do the handshake again. As Gon and Killua leave she wonders to herself when the next time she will see him again will be... Gon and Killua are on a ship sailing away from Whale Island, Gon suddenly hears a Fox Bear roar, looks to the forest cliff and sees Kon and all the animals saying goodbye and farewell. This then proceeds into chapter 70.
Thoughts?